C&C per req: (Viewing L -> R, T -> B)
1, 2, 3. Subject is either too centered or there is too much negative space around her (or both). Her feet are cropped and fill light is needed to compensate for the strongly backlit scene.
4. Snapshot.
To be frank, the first three have the impression of you having said to the child, "Stand there while I take your picture <camera set to 'Auto'> *Click*, carry on. Remember that a portrait is an image into which planning goes. That is, you need to think about all aspects of the image from exposure to composition to background. Let's look closely at 2/3 (other than the crop they're virtually identical) because they seem the strongest.
First get your exposure right. You've got a strongly backlit scene, so you need account for that either by spot-metering the subject (which will blow out the background) or by using fill light either in the form of a flash or reflector to reduce the dynamic range. As part of that, select a larger aperture which will render the background much less sharply focused and distracting. Next, compose the scene; shoulders square to the camera is almost never a good pose. Have her turn her body slightly to her right and look toward the camera, and then zoom in/out so that there's either much less empty space around her or she's less centered (search "rule of thirds").
They're a good start, but they're not quite "portraits" yet. Keep shooting!
Just my $00.02 worth - your mileage may vary.
~John